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What You Need to Know about Pregnancy and Exercise

As a soon-to-be personal trainer, you will likely one day be asked to work with a pregnant client. It’s important to know and understand this special population as best as possible to ensure the safety and effectiveness of their exercise experience. Use this blog as a starting point for learning some of the ins and outs of pregnancy and exercise.

Understanding Pregnancy’s Impact on the Body

What bodily changes occur during pregnancy?

Musculoskeletal System Changes

The average weight gain during pregnancy is 25-45 pounds, which increases force across joints of the body. This may cause increased joint discomfort, especially in the back, pelvis, hips and legs as your client’s center of gravity move upward and outward.

Cardiovascular System Changes

During pregnancy, the cardiovascular system changes as hormonal signals initiate relaxation and decreased responsiveness in most smooth muscle cells in a woman’s blood vessels. These hormonal changes result in an increase in the elasticity and volume of the entire circulatory system, affecting stroke volume.

More importantly as pregnancy progresses, a woman’s body position can affect her cardiovascular system both at rest and during exercise. After the first trimester, the supine position results in relative obstruction of venous return, and therefore decreased cardiac output. For this reason, supine positions should be avoided as much as possible during rest and exercise. In addition, motionless standing is associated with a significant decrease in cardiac output; therefore, this position should be avoided.

Respiratory System Changes

The delivery of oxygen to the mother and fetus is enhanced through improvements in lung function during pregnancy. At rest, an increase in the depth of each breath increases the amount of air inhaled by up to 50% or more, allowing for increased oxygen uptake and a 10-20% increase in baseline oxygen consumption. For those who maintain moderate-to-intense exercise programs throughout pregnancy, this causes a “training effect” in pregnant women, and may explain why there are reports of women who experience an improvement in competitive endurance performance after giving birth.

Thermoregulatory System Changes

A woman’s ability to eliminate heat improves during pregnancy due to a decrease of the body’s set point for normal temperature in early pregnancy and significant increase in blood to the skin.

Exercise performed before and during pregnancy may help to prevent obesity-related complications by decreasing BMI to a healthy range, preventing GDM and preeclampsia, and reducing the likelihood of excessive gestational weight gain.

Exercise during pregnancy has also been associated with a timely return to pre-pregnancy weight after delivery.

Weight Training appears to be safe and effective during pregnancy when low weights and multiple repetitions through a dynamic, controlled range of motion are performed. It would be wise to limit repetitive isometric or heavy-resistance weight-lifting, as well as any exercises that require the Valsava maneuver, which would increase abdominal pressure and, therefore, risk of complications for the fetus.

Flexibility training to maintain normal joint range of motion through individualized stretching exercises would be acceptable.

Nutritional considerations please refer to the American Dietetic Association’s position statement: “Nutrition and Lifestyle for a Healthy Pregnancy Outcome” (ADA, 2002) as your client will need to make sure she is addressing nutritional concerns by including additional calories to maintain homeostasis for herself and the baby.

Things to avoid:

Overly vigorous activity in the third trimester

Activities that have a high potential for contact

Activities with a high risk of falling

Activities with a risk of abdominal trauma

Exertion at altitude greater than 6,000 feet

Scuba diving

Maternal hyperthermia

Traditional heart rate-based methods to measure intensity because heart rate response is so viable during pregnancy. Instead the RPE (ratings of perceived exertion) scale should be used.

Programming Guidelines and Considerations for Postnatal Exercise

Research shows that physiological and morphological changes of pregnancy persist four to six weeks postpartum; therefore, pre-pregnancy exercise routines should be resumed gradually based on the woman’s physical capabilities. As highlighted in the ACE AHFS Manual, more detailed guidelines for postnatal exercise has been developed by Clapp (2002), who suggests that the initial goal of exercise (within the first six weeks) is to obtain personal time and redevelop a sense of control. This can be accomplished by doing the following:

Beginning slowly and increasing gradually

Avoiding excessive fatigue and dehydration

Supporting and compressing the abdomen and breasts

Stopping to evaluate if exercise hurts

Stopping exercise and seeking medical evaluation if the postpartum client is experiencing bright red vaginal bleeding that is heavier than a menstrual period

If my client is having a complicated pregnancy can she still exercise safely?

Exercise during and after pregnancy appears to be safe, but most importantly, ACE-professionals must require all pregnant clients to obtain a physician’s clearance before initiating an exercise program. For more information about working with pregnant clientele you may want to familiarize yourself with our Women’s Course Bundle which is offered for continuing education credit.

Alex Link is the Certification and Exam Registration Coordinator at ACE. She holds a BS in Sports Science with an emphasis in Sports Medicine, as well as an MS in Exercise Physiology. Additionally, ACE is an ACE-certified Personal Trainer and Health Coach.